ForCES Protocol Extensions
draft-ietf-forces-protoextension-01

Internet Engineering Task Force                            J. Hadi Salim
Internet-Draft                                         Mojatatu Networks
Intended status: Informational                            March 17, 2014
Expires: September 18, 2014

                       ForCES Protocol Extensions
                  draft-ietf-forces-protoextension-01

Abstract

   Experience in implementing and deploying ForCES architecture has
   demonstrated need for a few small extensions both to ease
   programmability and to improve wire efficiency of some transactions.
   This document describes extensions to the ForCES Protocol
   Specification[RFC 5810] semantics to achieve that end goal.

Status of this Memo

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   This Internet-Draft will expire on September 18, 2014.

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Table of Contents

   1.  Terminology and Conventions  . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
     1.2.  Definitions  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Problem Overview . . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Table Ranges . . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Error codes  . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Protocol Update Proposal . . . . . . . . . . . . . . . . . . .  6
     4.1.  Table Ranges . . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Error Codes  . . . . . . . . . . . . . . . . . . . . . . .  7
       4.2.1.  New Codes  . . . . . . . . . . . . . . . . . . . . . .  8
       4.2.2.  Vendor Codes . . . . . . . . . . . . . . . . . . . . .  8
       4.2.3.  Extended Result TLV  . . . . . . . . . . . . . . . . .  8
     4.3.  Large Object Dumping . . . . . . . . . . . . . . . . . . .  9
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11

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1.  Terminology and Conventions

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.2.  Definitions

   This document reiterates the terminology defined by the ForCES
   architecture in various documents for the sake of clarity.

      FE Model - The FE model is designed to model the logical
      processing functions of an FE.  The FE model proposed in this
      document includes three components; the LFB modeling of individual
      Logical Functional Block (LFB model), the logical interconnection
      between LFBs (LFB topology), and the FE-level attributes,
      including FE capabilities.  The FE model provides the basis to
      define the information elements exchanged between the CE and the
      FE in the ForCES protocol [RFC5810].

      LFB (Logical Functional Block) Class (or type) - A template that
      represents a fine-grained, logically separable aspect of FE
      processing.  Most LFBs relate to packet processing in the data
      path.  LFB classes are the basic building blocks of the FE model.

      LFB Instance - As a packet flows through an FE along a data path,
      it flows through one or multiple LFB instances, where each LFB is
      an instance of a specific LFB class.  Multiple instances of the
      same LFB class can be present in an FE's data path.  Note that we
      often refer to LFBs without distinguishing between an LFB class
      and LFB instance when we believe the implied reference is obvious
      for the given context.

      LFB Model - The LFB model describes the content and structures in
      an LFB, plus the associated data definition.  XML is used to
      provide a formal definition of the necessary structures for the
      modeling.  Four types of information are defined in the LFB model.
      The core part of the LFB model is the LFB class definitions; the
      other three types of information define constructs associated with
      and used by the class definition.  These are reusable data types,
      supported frame (packet) formats, and metadata.

      LFB Metadata - Metadata is used to communicate per-packet state
      from one LFB to another, but is not sent across the network.  The
      FE model defines how such metadata is identified, produced, and
      consumed by the LFBs, but not how the per-packet state is

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      implemented within actual hardware.  Metadata is sent between the
      FE and the CE on redirect packets.

      ForCES Component - A ForCES Component is a well-defined, uniquely
      identifiable and addressable ForCES model building block.  A
      component has a 32-bit ID, name, type, and an optional synopsis
      description.  These are often referred to simply as components.

      LFB Component - An LFB component is a ForCES component that
      defines the Operational parameters of the LFBs that must be
      visible to the CEs.

      ForCES Protocol - Protocol that runs in the Fp reference points in
      the ForCES Framework [RFC3746].

      ForCES Protocol Layer (ForCES PL) - A layer in the ForCES protocol
      architecture that defines the ForCES protocol messages, the
      protocol state transfer scheme, and the ForCES protocol
      architecture itself as defined in the ForCES Protocol
      Specification [RFC5810].

      ForCES Protocol Transport Mapping Layer (ForCES TML) - A layer in
      ForCES protocol architecture that uses the capabilities of
      existing transport protocols to specifically address protocol
      message transportation issues, such as how the protocol messages
      are mapped to different transport media (like TCP, IP, ATM,
      Ethernet, etc.), and how to achieve and implement reliability,
      ordering, etc. the ForCES SCTP TML [RFC5811] describes a TML that
      is mandated for ForCES.

2.  Introduction

   Experience in implementing and deploying ForCES architecture has
   demonstrated need for a few small extensions both to ease
   programmability and to improve wire efficiency of some transactions.
   This document describes a few extensions to the ForCES Protocol
   Specification [RFC5810] semantics to achieve that end goal.

   This document describes and justifies the need for 2 small extensions
   which are backward compatible.  The document also clarifies on top of
   [RFC5810] how dumping of large components is achieved.

   1.  A table range operation to allow a controller or control
       application to request an arbitrary range of table rows.

   2.  Improved Error codes returned to the controller (or control
       application) to improve granularity of existing defined error

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       codes.

   3.  FE response to a GET request (example to a large table) may not
       fit in one PL message, for example due to limited TLV space.

3.  Problem Overview

   In this section we present sample use cases to illustrate the
   challenge being addressed.

3.1.  Table Ranges

   Consider, for the sake of illustration, an FE table with 1 million
   reasonably sized table rows which are sparsely populated.  Assume,
   again for the sake of illustration, that there are 2000 table rows
   sparsely populated between the row indices 23-10023.

   ForCES GET and DEL requests sent from a controller (or control app)
   are prepended with a path to a component and sent to the FE.  In the
   case of indexed tables, the component path can either be to a table
   or a table row index.  The approaches for retrieving or deleting a
   sizeable number of table rows is at the programmatically level (from
   an application point of view) unfriendly, tedious, and abusive of
   both compute and bandwidth resources.

   As an example, a control application attempting to retrieve the first
   2000 table rows appearing between row indices 23 and 10023 can
   achieve its goal in one of:

   o  Dump the whole table and filter for the needed 2000 table rows.

   o  Send upto 10000 ForCES PL requests with monotonically incrementing
      indices and stop when the needed 2000 entries are retrieved.

   o  If the application had knowledge of which table rows existed (not
      unreasonable given the controller is supposed to be aware of state
      within an NE), then the application could take advantage of ForCES
      batching to send fewer large messages (each with different path
      entries for a total of two thousand).

   As argued, while the above options exist - all are tedious.

3.2.  Error codes

   [RFC5810] has defined a generic set of error codes that are to be
   returned to the CE from an FE.  Deployment experience has shown that
   it would be useful to have more fine grained error codes.  As an

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   example, the error code E_NOT_SUPPORTED could be mapped to many FE
   error source possibilities that need to be then interpreted by the
   caller based on some understanding of the nature of the sent request.
   This makes debugging more time consuming.

4.  Protocol Update Proposal

   This section describes proposals to update the protocol for issues
   discussed in Section 3

4.1.  Table Ranges

   We propose to add a Table-range TLV (type ID 0x117) that will be
   associated with the PATH-DATA TLV in the same manner the KEYINFO-TLV
   is.

      +---------------------+---------------------+
      |  Type (0x117)       |       Length        |
      +---------------------+---------------------+
      |                Start Index                |
      +-------------------------------------------+
      |                 End Index                 |
      +-------------------------------------------+

                Figure 1: ForCES table range request Layout

   Figure 1 shows how this new TLV is constructed.

      OPER = GET
             PATH-DATA:
               flags = F_SELTABRANGE,  IDCount = 2, IDs = {1,6}
               TABLERANGE-TLV content = {11,23}

                   Figure 2: ForCES table range request

   Figure 2 illustrates a GET request for a range of rows 11 to 23 of a
   table with component path of "1/6".

   Path flag of F_SELTABRANGE (0x2 i.e bit 1, where bit 0 is F_SELKEY as
   defined in RFC 5810) is set to indicate the presence of the
   TABLERANGE-TLV.  The pathflag bit F_SELTABRANGE can only be used in a
   GET or DEL and is mutually exclusive with F_SELKEY.  The FE MUST
   enforce those constraints and reject a request with an error code of
   E_INVALID_TFLAGS with a description of what the problem is (refer to
   Section 4.2).

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   The TABLERANGE-TLV contents constitute:

   o  A 32 bit start index.  An index of 0 implies the beggining of the
      table row.

   o  A 32 bit end index.  A value of 0xFFFFFFFFFFFFFFFF implies the
      last entry.

   The response for a table range query will either be:

   o  The requested table data returned (when at least one referenced
      row is available); in such a case, a response with a path pointing
      to the table and whose data content contain the row(s) will be
      sent to the CE.  The data content MUST be encapsulated in
      sparsedata TLV.  The sparse data TLV content will have the "I" (in
      ILV) for each table row indicating the table indices.

   o  An EXTENDEDRESULT-TLV (refer to Section 4.2.3) when:

      *  Response is to a range delete request.  The Result will either
         be:

         +  A success if any of the requested-for rows is deleted

         +  A proper error code if none of the requested for rows can be
            deleted

      *  data is absent where the result code of E_EMPTY with an
         optional content string describing the nature of the error
         (refer to Section 4.2).

      *  When both a path key and path table range are reflected on the
         the pathflags, an error code of E_INVALID_TFLAGS with an
         optional content string describing the nature of the error
         (refer to Section 4.2).

      *  other standard ForCES errors (such as ACL constraints trying to
         retrieve contents of an unreadable table), accessing unknown
         components etc.

4.2.  Error Codes

   We propose several things:

   1.  A new set of error codes.

   2.  Allocating currently reserved codes for vendor use.

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   3.  A new TLV, EXTENDEDRESULT-TLV (0x118) that will carry a code
       (which will be a superset of what is currently specified in RFC
       5812) but also an optional cause content.  This is illustrated in
       Figure 3.

4.2.1.  New Codes

   EXTENDEDRESULT-TLV Result Value is 32 bits and is a superset of RFC
   5810 Result TLV Result Value.  The new version code space is 32 bits
   as opposed to the RFC 5810 code size of 8 bits.

   +------------+-------------------------+----------------------------+
   | Code       | Mnemonic                | Details                    |
   +------------+-------------------------+----------------------------+
   | 0x100      | E_EMPTY                 | Table is empty             |
   | 0x101      | E_INVALID_TFLAGS        | Invalid table flags        |
   | 0x102      | E_INVALID_OP            | Requested operation is     |
   |            |                         | invalid                    |
   | 0x103      | E_CONGEST_NT            | Node Congestion            |
   |            |                         | notification               |
   | 0x104      | E_COMPONENT_NOT_A_TABLE | Component not a table      |
   | 0x105      | E_PERM                  | Operation not permitted    |
   | 0x107      | E_BUSY                  | System is Busy             |
   | 0x108      | E_TIMED_OUT             | A time out occured while   |
   |            |                         | processing the message     |
   | 0x106      | E_UNKNOWN               | A generic catch all error  |
   |            |                         | code. Carries a string to  |
   |            |                         | further extrapolate what   |
   |            |                         | the error implies.         |
   +------------+-------------------------+----------------------------+

                            Table 1: New codes

4.2.2.  Vendor Codes

   Codes 0x18-0xFE are reserved for use as vendor codes.  Since these
   are freely available it is expected that the FE and CE side will both
   understand/interpret the semantics of any used codes.

4.2.3.  Extended Result TLV

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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Type = EXTENDEDRESULT-TLV   |              Length           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Result Value                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    Optional Cause content                     |
       .                                                               .
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 3: EXTENDEDRESULT-TLV

   o  Like all other ForCES TLVs, the EXTENDEDRESULT-TLV is expected to
      be 32 bit aligned.

   o  The Result Value derives and extends from the same current
      namespace as specified in RFC 5810, section 7.1.7.  The main
      difference is that we now have 32 bit result value (as opposed to
      the old 8 bit).

   o  The optional result content is defined to further disambiguate the
      result value.  It is expected Utf-8 values to be used.  However,
      vendor specific error codes may choose to specify different
      contents.  Additionally, future codes may specify cause contents
      to be of types other than string..

   o  It is recommended that the maximum size of the cause string should
      not exceed 32 bytes.  We do not propose the cause string be
      standardized.

   XXX: Backward compatibility may require that we add a FEPO capability
   to advertise ability to do extended results so that the CE is able to
   interpret the results and a FEPO compatibility flag to define what
   TLV setting would be used.  Alternatively, the backward compatibility
   can be made a configuration option (which helps reduce clutter on
   FEPO LFB given that it is expected that in the future it makes sense
   for implementations to support only EXTENDEDRESULT-TLVs).

4.3.  Large Object Dumping

   Imagine a GET request to a path that is a table i.e a table dump.
   Such a request is sent to the FE with a specific correlator, say X.
   Imagine this table to have a large number of entries at the FE.  For
   the sake of illustration, lets say millions of rows.  This requires
   that the FE delivers the response over multiple messages, all using
   the same correlator X.

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   RFC 5810 does not describe how a GET response is to indicate "I have
   more messages coming for this correlator".

   Implementation experience indicates we can use the transaction flags
   to indicate that a GET response is the beginning, middle or end of a
   multi-part message.  In other words we mirror the effect of an atomic
   transaction sent by a CE to an FE.

   XXX: Add in the next update diagram and details of how this takes
   place.

5.  Acknowledgements

   TBA

6.  IANA Considerations

   This document registers two new top Level TLVs and two new path
   flags.

   The following new TLVs are defined:

   o  TABLERANGE-TLV (type ID 0x117)

   o  EXTENDEDRESULT-TLV (type ID 0x118)

   The following new path flags are defined:

   o  F_SELTABRANGE (value 0x2 i.e bit 1)

   The Defined Result Values are changed:

   o  codes 0x18-0xFE are reserved for vendor use.

   o  codes 0x100-102 are defined by this document.

7.  Security Considerations

   TBD

8.  References

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8.1.  Normative References

   [RFC3746]  Yang, L., Dantu, R., Anderson, T., and R. Gopal,
              "Forwarding and Control Element Separation (ForCES)
              Framework", RFC 3746, April 2004.

   [RFC5810]  Doria, A., Hadi Salim, J., Haas, R., Khosravi, H., Wang,
              W., Dong, L., Gopal, R., and J. Halpern, "Forwarding and
              Control Element Separation (ForCES) Protocol
              Specification", RFC 5810, March 2010.

   [RFC5811]  Hadi Salim, J. and K. Ogawa, "SCTP-Based Transport Mapping
              Layer (TML) for the Forwarding and Control Element
              Separation (ForCES) Protocol", RFC 5811, March 2010.

   [RFC5812]  Halpern, J. and J. Hadi Salim, "Forwarding and Control
              Element Separation (ForCES) Forwarding Element Model",
              RFC 5812, March 2010.

8.2.  Informative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

Author's Address

   Jamal Hadi Salim
   Mojatatu Networks
   Suite 400, 303 Moodie Dr.
   Ottawa, Ontario  K2H 9R4
   Canada

   Email: hadi@mojatatu.com

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